1. Technical Field
The present invention relates to a piezoelectric element drive circuit and various apparatuses such as a robot including a piezoelectric element drive circuit.
2. Related Art
In the related art, a piezoelectric actuator (piezoelectric drive device) using a piezoelectric element is known (for example, JP-A-2004-320979). According to a basic configuration of the piezoelectric drive device, four piezoelectric elements are configured to be arranged in two rows and two columns on two surfaces of a reinforcing plate. Eight piezoelectric elements in total are disposed on both sides of the reinforcing plate. Each of the piezoelectric elements is a unit which interposes each piezoelectric substance between two electrodes. The reinforcing plate is used as one electrode of the piezoelectric element. One end of the reinforcing plate has a protrusion portion disposed in order to rotate a rotor by coming into contact with the rotor serving as a driven body. If an AC voltage is applied to the two piezoelectric elements arranged at opposite angles among the four piezoelectric elements, the two piezoelectric elements perform expansion and contraction movement. In response to the movement, the protrusion portion of the reinforcing plate performs reciprocating movement or elliptical movement. Then, in response to the reciprocating movement or the elliptical movement of the protrusion portion of the reinforcing plate, the rotor serving as the driven body is rotated in a predetermined rotation direction. The rotor can be rotated in the opposite direction by switching from the two piezoelectric elements to which the AC voltage is applied to the other two piezoelectric elements.
In the related art, as the piezoelectric substance used for the piezoelectric drive device, a so-called bulky piezoelectric substance is used. The “bulky piezoelectric substance” described herein means a piezoelectric substance whose thickness is 100 μm or greater. The reason for using the bulky piezoelectric substance is to increase the thickness of the piezoelectric substance in order to sufficiently strengthen force applied to the driven body from the piezoelectric drive device.
According to the piezoelectric drive device in the related art, two piezoelectric elements arranged at opposite angles are connected in parallel. Consequently, there is a problem in that the piezoelectric drive device has a large electrostatic capacity and thus needs a large amount of currents in driving the piezoelectric drive device.
When the piezoelectric drive device is used by being accommodated in a small space (for example, inside a joint of a robot), there is a possibility that a wiring space may be insufficient in the piezoelectric drive device using the piezoelectric substance in the related art. Accordingly, there is a demand for a thinner piezoelectric substance. However, the electrostatic capacity is inversely proportional to a distance between the electrodes interposing the piezoelectric substance therebetween. For this reason, if the piezoelectric substance becomes thinner, the electrostatic capacity is forced to increase, thereby causing a problem of increased power consumption.